This disclosure incorporates herein by reference, in its entirety, U.S. Pat. No. 7,207,365, entitled “Central Tire Inflation System Rotary Air Union.”
Tire pressure maintenance is and has always been important to proper operation of a vehicle. The trucking industry has promoted this subject as a means to increase tire life and fuel economy, while reducing downtime and maintenance costs due to flat tires or the like. A tire blowout on the road can be unsafe for a number of different reasons, including difficulty controlling the vehicle as well as debris left on the roadway that can be hazardous to other drivers. Proper tire pressure can decrease the possibility of tire failures and may increase safe operation for the vehicle driver and other drivers on the road.
Various CTISs have been designed and are the subject of numerous patents that accomplish the objective of tire pressure maintenance. The most common systems in the heavy truck industry are designed for trailers. Heavy trucks typically include a tractor and a trailer. Often, the trailer axles are hollow with axle ends that commonly have a through bore. The hollow axle provides a conduit to supply air pressure to the wheel end. Delivery of air via a hose is more challenging for steer axles and drive axles in part due to typically solid spindles on steer axles and solid rotating shafts inside drive axles. In all cases, steer, driven, and trailer, the wheel end assembly includes a lubrication area between the axle and the wheel. This may require plugging the through bore in the axle end and covering the end of the axle with a hubcap attached to the wheel. The wheel is supported on the axle end by wheel bearings. The bearings require lubrication and the integrity of the lubrication area is essential in maintaining the operability and life of the wheel end assembly. In order to provide pressurized air to the rotating tires, the CTIS may include a rotary union in the same general location as the bearings. In most cases, the CTIS is in or adjacent to the lubrication area between the stationary axle and the wheel. The CTIS should not allow pressurized air into the lubrication area. Pressurized air in the lubrication area may cause the lubricating oil to be forced past the wheel seals by air pressure leading to bearing failure and consequently catastrophic wheel failure.
Two methods are commonly used to supply pressurized air to the end of a trailer axle, pressurize the axle itself, or use a smaller conduit, such as an air hose, inserted within the axle. In either case, the air pressure at the end of the axle is then communicated from the stationary axle to the rotating wheel by the use of a rotary union.
The rotary air union assembly in combination with a regulated air pressure source functions to deliver air from the stationary axle to one or more rotating tires. The regulated air pressure source uses vehicle air pressure typically supplied by the tractor's air compressor or the trailer's air pressure tanks, which may also provide a reservoir of air (or other gas) for operation of the pneumatic brakes. The regulated air pressure source for the CTIS may include a filter, a regulator, air tubing, and fittings. A flow or pressure sensor may be included to sense air supply to the tires. Also, an isolation valve may be provided to isolate the CTIS from the regulated air pressure source. If the CTIS includes a sensor, generally, a light is included to alert the driver or operator that the CTIS is supplying air to the tires, which often needs to be observed by the driver by use of the rearview mirror.
The primary seal within the rotary air union also takes many forms; a spring loaded face seal, o-ring seals, u-cup seals, or packing material seals. The primary seal is a key element of the rotary union; however, even in the best conditions, air can escape from the primary seal and pressurize the lubrication area. Vents to atmosphere have been disclosed including the vent chamber, vent passageway, and check valve, such as described in the above-referenced U.S. Pat. No. 7,207,365.
A further function of a typical rotary union is to supply air from the stationary axle to the rotating wheel and tire when misalignment between the two is present. Varied approaches to this challenge have been disclosed. In each case, the associated seals and connections are torque carrying elements between or within the stationary and rotating components of the rotary union.
Prior solutions drive torque through o-ring seals, conduits, threaded connections, and fittings, for example. In the referenced patent, U.S. Pat. No. 7,207,365, a coupling is claimed to limit the application of rotational torque on the flexible conduit that is supplying air to the rotary union.
Tire pressure monitoring systems are available to sense, report, and optionally record the current status and pressure history of one or more tires. An example is the BAT RF® system provided by Stemco LP of Longview, Tex. Various aspects of the present disclosure provide the ability to integrate a monitoring system into the maintenance system.
Thus, against the above background, it would be desirable to provide an improved device to couple the rotating and non-rotating parts of a CTIS system to reduce the effect of torque on the various components.
While the above-identified drawing figures set forth one exemplary embodiment, other embodiments of the present invention are also contemplated, as noted throughout. The technology of the present application is described by way of representative examples and should not be construed as limiting. Numerous other modifications and embodiments within the spirit and scope of the technology of the present application are incorporated herein.